1. Field of the Invention
The present invention relates to pattern recognition systems (PRS) and location of a pattern or object after locating a reference teach object whose location is known. More particularly, the present invention comprises a substantially improved method for locating objects whose size varies from the reference teach object.
The present invention is an improvement of a prior art pattern recognition system (PRS) incorporated into Models 1482 and 1484 automatic wire bonder sold by Kulicke and Soffa Industries, Inc. of Willow Grove, Pa.
2. Description of the Prior Art
The present invention is an improvement of a prior art Model 860 pattern recognition system (PRS) incorporated into Models 1482 and 1484 automatic wire bonder sold by Kulicke and Soffa Industries, Inc. of Willow Grove, Pa.
Numerous different types of PRS are in commercial use today. Almost all such systems employ reference characters, reference objects, or reference patterns which are learned by the PRS and stored as electrical signals in analog or digital format.
When the PRS attempts to find or identify an unknown object or pattern, it is sensed in the same way the reference object was sensed to produce electrical signals that may be compared to the reference object signals. These character recognition techniques are over 50 years old and are classified in International Class GO6r, subclass 9/00 plus which corresponds to U.S. Class 382, subclasses 10 and 16 to 30.
When the PRS is employed for both object or pattern recognition and position location, more precise techniques are usually employed. The reference object or reference pattern has a known position which is also stored as electrical signals. The object or pattern to be located is effectively moved until it matches the reference pattern and the amount of movement necessary to effect this match is equal to the displacement of the object being located from the reference object. The use of PRSs to locate the position of an object are over 20 years old and are classified in International Class GO6K, subclass 9/32 plus which corresponds to U.S. Class 382, subclass 8 to 48. While some of the systems are more effective than others, none of the systems provide results which are so reliable that they are compatible with the accuracy required on automatic semiconductor production lines. As an example, during automatic wire bonding, it is necessary to locate eye points or reference points of a chip within a fraction of 1-thousandth of inch which is possible when the pattern on the reference chip and the chips to be wire bonded are the same size. However, the chip is die bonded to a lead frame. The stamped or screen printed lead frames differ greatly in size and it is virtually impossible to locate an identical eye point or reference on successive lead frames which differ one from the other in both size and shape.
It would be desirable to provide a simple and effective method and apparatus for locating eye points or reference points on objects whose size varies from object to object as well as from the reference object.